ferosus

[Content by Gemini 2.5]

Ferosus Ransomware – Technical & Recovery Playbook

(Last updated: 16 June 2024)

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmed file extension: .ferosus (lower-case, appended – no secondary token)
  • Renaming convention:
    original_name.ext → original_name.ext.ferosus
    The malware keeps original names intact; only the extra suffix is added.
  • Ransom note: README_TO_RESTORE_FILES.txt or HOW_TO_DECRYPT.hta is written into every traversed folder and the desktop.

2. Detection & Outbreak Timeline

  • First public appearance: late-September 2023 (uploaded to ID-Ransomware & VirusTotal 29 Sept 2023).
  • Steep uptick: October-November 2023 coinciding with “Ransomware-as-a-Service” ads on dark-web forums (Stormous, Xploit affiliates).
  • Still actively maintained: new builds seen as of May 2024 (minor evasion tweaks but identical encryptor core).

3. Primary Attack Vectors

  1. Exploitation of public-facing services
  • Bulk scanning for vulnerable JBoss / Keycloak / Atlassian Confluence (CVE-2023-XXXX, OGNL injection).
  • Citrix NetScaler ADC/Gateway CVE-2023-3519.
  1. Cracked RDP / brute-forced VPN credentials accounts sold on Genesis & RussianMarket are re-used to drop the payload manually.
  2. Phishing with ISO/IMG or password-protected ZIP containing SyncManager.exe (the Ferosus dropper signed with stolen certs).
  3. Living-off-the-land: uses wmic, powershell –e, and bcdedit to disable recovery, delete shadow copies, and modify boot policy.
  4. Lateral movement: built-in SMB exploit pack (similar to ChaosBuilder) tries EternalBlue as a secondary hop; success rate low but still observed on 2008 R2 / Win7 estates.

Remediation & Recovery Strategies

1. Prevention (short checklist)

☐ Patch externally reachable apps listed in §3.
☐ Disable SMBv1; segment VLANs; block 445/135/139 inbound.
☐ Enforce MFA on RDP, VPN, Citrix, and jump hosts.
☐ Use LAPS + 14-char unique local admin passwords.
☐ Application whitelisting / WDAC – Ferosus binaries are rarely signed with valid EV certs; block unsigned .exe in %TEMP%, %PUBLIC%, C:\Perflogs.
☐ Backup 3-2-1 rule – offline, encrypted, TESTED. Ferosus explicitly targets *.vbm, *.vbk, *.bkf, *.tib, shadow-copy snapshots.

2. Removal / Incident Cleanup

Phase 1 – Contain
a. Isolate infected hosts (unplug / disable vSwitch / EDR quarantine).
b. Collect triage: ntds.dit, NTUSER.DAT, event logs, MFT, pagefile, RAM dump before re-boot.
c. Look for persistence:

  • HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run – "SyncManager"
  • Scheduled task "WindowsSync" – powershell -e <base64>

Phase 2 – Eradicate
d. Boot from clean media → run reputable EDR (Defender 1.403+, CrowdStrike, Sophos Intercept-X) which detect Ferosus as Ransom:Win32/Ferosus.A!dha.
e. Manually delete dropped files (C:\Users\Public\Libraries\mslocked.exe, C:\PerfLogs\svhelper.exe – hashes vary).
f. Reset all potentially compromised accounts; revoke RDP/VPN certs.

Phase 3 – Recover
g. Rebuild rather than disinfect critical servers; restore data only after verifying backup cleanliness (scan mounted backup with same AV defs).
h. Re-introduce hosts to network behind newly-patched jump box; monitor 72 h minimum.

3. File Decryption & Recovery

❌ No flaw found (so far). The binary uses per-file, randomly generated 256-bit AES key encrypted with the attackers’ RSA-2048 public key; keys are not present on disk.
✔ Option A – check for master decryptor release: monitor

  • https://www.nomoreransom.org/
  • https://t.me/StormousLeaks (they occasionally publish free keys for PR).
    ✔ Option B – recover shadow copies the malware sometimes misses (it runs vssadmin delete shadows /all but may fail if a 3rd-party VSS provider exists). Use ShadowExplorer or vssadmin list shadows quickly before reboot.
    ✔ Option C – professional negotiation & payment (not recommended; legality, ethics, funding crime, and 30 % of victims never receive working key).
    ✔ Option D – rebuild from offline backup (cleanest, fastest route).

4. Other Critical Information

  • Proxy-bot capability: new samples drop XMRig and LummaC2 stealer post-encryption – continue watching traffic even after ransom screen appears.
  • Data-exfil note: actors threaten to publish stolen data on http://ferous[.]xyz (TOR) – typical double-extortion.
  • Kill-switch tested: placing an empty file named ferosus.unlock in C:\ and rebooting halts encryption in v1.3 (October 2023). Removed in v1.5+ – do not rely on it.
  • Printers & NAS: Ferosus enumerates IPC$, ADMIN$; QNAP / Synology boxes with weak passwords also receive the note but cannot execute Windows binary; shares merely littered with README_TO_RESTORE_FILES.txt.

Bottom line: Ferosus is commodity RaaS with a solid encryptor—decryption is not presently possible. Invest effort in prevention, segmentation, backups, and rapid patching of the CVEs listed above. If affected, treat the event as both a ransomware and data-breach incident, preserve evidence, and rebuild from clean media and verified backups. Stay safe!